Flexible perovskite thin film, preparation method thereof and flexible perovskite solar cell

Abstract

The invention belongs to the technical field of solar cells, and particularly relates to a flexible perovskite thin film, a preparation method thereof and a flexible perovskite solar cell. The method comprises the following steps: preparing a mesoporous layer on a rigid substrate, and spin-coating a methylamine solution on the mesoporous layer to obtain a covering layer; preparing an electron transport layer on a flexible substrate, spin-coating the electron transport layer with a perovskite precursor solution, and dropwise adding an inversion solvent before spin-coating is finished to obtain a perovskite precursor wet film; covering the perovskite precursor wet film with a covering layer, so that the covering layer and the perovskite precursor wet film form a closed space, and water is prevented from entering the closed space; meanwhile, through annealing treatment, under the action of auxiliary nucleation and diffusion recrystallization of the covering layer, the perovskite thin film is obtained; and cooling and removing the hard substrate to obtain the flexible perovskite thin film on the flexible substrate. The prepared perovskite thin film is good in stability, high in photoelectric conversion efficiency and suitable for being used as a material of a perovskite solar cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and in particular relates to a flexible perovskite film and a preparation method thereof, and a flexible perovskite solar cell. Background Art

[0002] Flexible perovskite solar cells, or F-PSCs, have great potential for commercial applications due to their excellent flexibility, light weight, and low-cost roll-to-roll manufacturing, such as foldable electronics, wearable electronic textiles, large industrial roofs, and power sources for unmanned aerial vehicles. In recent years, F-PSCs have also made significant progress in power conversion efficiency, with small-area flexible perovskite solar cells achieving a photoelectric conversion efficiency of 24.08%. However, there are still some problems, such as oxygen humidity stability, environmental impact, and toxicity.

[0003] Currently, the preparation of highly efficient and stable F-PSCs needs to be done under a strict inert atmosphere, such as in a nitrogen glove box. This is mainly because the perovskite film in F-PSCs is extremely sensitive to moisture in the surrounding air, which can easily lead to initial hydration, followed by destructive phase transitions, destruction of the crystal framework, and decomposition. The harsh conditions for the preparation of perovskite films complicate the manufacturing process of F-PSCs devices, increase costs, and pose a great challenge to the large-area manufacturing of perovskite films.

[0004] The existing technology continuously optimizes the preparation method of perovskite film to adapt to various environmental conditions. Meng's team (Meng, H., Mao, K., Cai, F. et al. Inhibition of halide oxidation and deprotonation of organic cations with dimethylammonium formate for air-processed perovskite solar cells. Nat Energy 9, (2024): 536-547.) introduced DMAFo as an ionic liquid stabilizer to protect the crystallization process of the film in the air, thereby improving the crystallinity of the film. Zhuang et al. (Zhuang J, Liu C, Kang B, et al. Rapid Surface Reconstruction in Air-Processed Perovskite SolarCells by Blade Coating [J]. Advanced Materials, 2024, 36 (6): 2309869.) used a new modifier DPGABr to scrape on the film surface in an air environment, and obtained excellent long-term stability; Yan et al. (Yan, Luyao, et al. "Fabrication of perovskite solar cells in ambient air by blocking perovskite hydration with guanabenz acetate salt." Nature Energy 8.10 (2023): 1158-1167.) used guanidine acetate as an additive to prevent the hydration of perovskite and obtain perovskite solar cells in an air environment. However, the above prior art research is based on rigid substrates, and there is still a lack of effective solutions for preparing perovskite films on flexible substrates and in an air environment. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a flexible perovskite film and a preparation method thereof, and a flexible perovskite solar cell.

[0006] In order to obtain high-efficiency F-PSCs prepared in an air environment on a flexible substrate, the present invention is based on the research on a rigid substrate in the prior art, optimizes the crystallization of the perovskite film through an additive strategy, and combines a confined space annealing strategy to prevent the influence of moisture in the air environment on the perovskite film. The present invention prepares a mesoporous layer on a rigid substrate, and uses a methylamine solution as an additive, and uses the additive to prepare a solution and apply it to the mesoporous layer to form a covering layer; then the perovskite precursor solution is applied to the electron transport layer of the flexible substrate to form a perovskite wet film; and the covering layer is covered on the perovskite wet film, and the crystallization process of the perovskite film during the annealing process is controlled by the covering layer to obtain a smooth and pinhole-free perovskite film.

[0007] The first object of the present invention is to provide a method for preparing a flexible perovskite film, comprising the following steps:

[0008] Step 1: prepare a mesoporous layer on a hard substrate, and spin-coat a methylamine solution onto the mesoporous layer to obtain a covering layer.

[0009] It should be noted that the present invention first prepares a mesoporous layer on a hard substrate, so that the methylamine solution can be better attached to the mesoporous layer; this is because the mesoporous layer has certain pores and has a certain adsorption effect on the methylamine solution, and the methylamine solution can penetrate into the pores; when the covering layer formed by the methylamine solution is covered on the perovskite precursor wet film for annealing, the methylamine solution and the perovskite precursor wet film are in contact and diffused, promoting crystallization to obtain a high-quality perovskite film; at the same time, after high-temperature annealing, the mesoporous layer will not interact with the perovskite film. Preferably, the mesoporous layer is a TiO2 layer, and the thickness of the mesoporous layer is 50nm to 100nm. In addition, it should be noted that the methylamine solution cannot be directly coated on a hard substrate, and the methylamine solution cannot adhere to a smooth glass substrate.

[0010] Preferably, the methylamine solution is a methylammonium chloride solution, a methylammonium iodide solution or a methylammonium thiocyanate solution. When the methylamine solution is a methylammonium chloride solution, the low-temperature film formation mechanism of the α-FAPbI3 perovskite film is the auxiliary nucleation of methylamine and the Cl - Induced diffusion recrystallization. During the diffusion recrystallization process, methylamine perovskite first nucleates and crystallizes in the middle area of ​​the substrate due to its lower formation energy; - In the presence of Cl - The interaction between FA and I in the perovskite film is enhanced. Methylamine can be replaced by formamidine in the perovskite precursor film at 100°C; the replaced methylamine group diffuses from the center of the film to the periphery and recrystallizes again. This cycle is repeated to eventually form a pure α-phase FAPbI3 perovskite film. By delaying the volatilization of methylammonium chloride and blocking the entry of water, methylamine can promote the nucleation of methylamine-based perovskite. -It can effectively reduce the phase transition temperature of the perovskite film from the δ phase to the α phase. - The synergistic effect of the above mentioned α-phase FAPbI3 films can be used to obtain high-quality α-phase FAPbI3 films. More preferably, the methylamine solution is a methylammonium chloride solution.

[0011] When the methylamine solution is methylammonium iodide solution, the film formation mechanism of α-FAPbI3 perovskite film is the auxiliary nucleation of methylamine. Methylamine reacts with [PbI6] in the perovskite precursor film. 4- Octahedral nucleation crystallization, and the formation of α-phase methylamine perovskite in the middle area of ​​the substrate, the iodide ions in methylammonium iodide can form a stable lead-halide bond with the lead ions in the perovskite structure to form FAPbI3 perovskite film; when the methylamine solution is methylammonium thiocyanate solution, the film formation mechanism of α-FAPbI3 perovskite film is the auxiliary nucleation of methylamine, methylamine and perovskite precursor film [PbI6] 4- Octahedrons nucleate and crystallize to form α-phase methylamine perovskite. The thiocyanate ions in methylammonium thiocyanate interact with the lead ions in the perovskite precursor film. The sulfur atoms or nitrogen atoms of the thiocyanate ions can form coordination bonds with the lead ions to form FAPbI3 perovskite film.

[0012] Preferably, the methylamine solution is formed by dissolving methylammonium chloride, methylammonium iodide or methylammonium thiocyanate in isopropanol, and the concentration of the methylamine solution is 4.9 mg / mL to 5.1 mg / mL.

[0013] Step 2: prepare an electron transport layer on a flexible substrate, spin-coat the perovskite precursor solution onto the electron transport layer, and drop a reverse solvent before the spin coating is completed to obtain a perovskite precursor film.

[0014] Preferably, the concentration of the perovskite precursor solution is 1 mol / L to 2 mol / L.

[0015] Preferably, the perovskite precursor solution is composed of a solute and a solvent; wherein the solute includes formamidine halide and lead salt, and the solvent is dimethylformamide and N-methylpyrrolidone.

[0016] Preferably, the thickness of the flexible perovskite film is 500 nm.

[0017] Step 3, covering the perovskite precursor film with a covering layer so that the covering layer and the perovskite precursor film form a closed space to block the entry of moisture; at the same time, through annealing treatment, under the auxiliary nucleation and diffusion recrystallization of the covering layer, a perovskite film is obtained; after cooling, the hard substrate is removed to obtain a flexible perovskite film on a flexible substrate.

[0018] The present invention forms a covering layer with a methylamine solution and covers the perovskite precursor film, thereby delaying the volatilization of the methylamine solution in the covering layer, thereby blocking the entry of moisture; at the same time, the methylamine in the methylamine solution can promote the nucleation of methylamine-based perovskite; in addition, the Cl in methylammonium chloride - It can effectively reduce the phase transition temperature of the perovskite precursor film from the δ phase to the α phase, that is, reduce the annealing temperature; by methylamine and Cl - The synergistic effect of the annealing treatment can obtain a high-quality α-phase FAPbI3 perovskite film. Preferably, the annealing treatment temperature is 70°C to 100°C.

[0019] The full name of polyethylene naphthalate in English is Polyethylene Naphthalate, abbreviated as PEN in English. PEN is a polymer film that is generally more resistant to high temperatures and has better mechanical properties. When a thin indium tin oxide conductive film is coated on the surface of PEN, the resulting ITO-PEN structure can maintain the high temperature resistance and mechanical properties of PEN to a certain extent, while also having conductivity. The full name of fluorine-doped tin oxide in English is Fluorine-doped Tin Oxide, abbreviated as FTO in English. FTO-PEN refers to a layer of FTO film coated on PEN. Preferably, the flexible substrate is an ITO-PEN or FTO-PEN transparent electrode, and the rigid substrate is glass.

[0020] The second object of the present invention is to provide a flexible perovskite film prepared by the above preparation method.

[0021] The third object of the present invention is to provide a flexible perovskite solar cell prepared by the above-mentioned flexible perovskite film.

[0022] Preferably, the flexible perovskite solar cell comprises: a flexible substrate, an electron transport layer, a perovskite film, a hole transport layer and a metal electrode.

[0023] It should be noted that the present invention uses the electron transport layer of a flexible substrate as a base to prepare a perovskite film, prepares a hole transport layer on the perovskite film, and finally prepares a metal electrode on the hole transport layer to obtain a flexible perovskite solar cell.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention has developed a method for preparing a dense, continuous, flexible perovskite film on a flexible substrate and in humid air. The present invention prepares a mesoporous layer on a hard substrate, and forms a covering layer on the mesoporous layer using a methylamine solution; prepares an electron transport layer on a flexible substrate, and forms a perovskite precursor film on the electron transport layer using a perovskite precursor solution; and covers the perovskite precursor film with the covering layer, and performs an annealing treatment to delay the volatilization of the methylamine solution in the covering layer, thereby blocking the entry of moisture; at the same time, the methylamine groups in the covering layer react with [PbI6] 4- Octahedral nucleation crystallization is used to promote the nucleation of methylamine perovskite and form α-phase methylamine perovskite in the middle area of ​​the substrate to form an α-phase FAPbI3 perovskite film.

[0026] In the present invention, when methyl ammonium chloride is used as an additive to form a covering layer on the perovskite precursor film, - In the presence of Cl - The interaction between FA and I in the perovskite film is enhanced. Methylamine can be replaced by formamidine in the perovskite precursor film at 100 °C. The replaced methylamine group diffuses from the center of the film to the periphery and recrystallizes again to form a pure α-phase FAPbI3 perovskite film. At the same time, Cl in methylammonium chloride - The phase transition temperature of the perovskite precursor film from the δ phase to the α phase was effectively reduced, and the annealing temperature was reduced to 100°C to be compatible with the tolerance temperature of the flexible substrate and reduce the residual stress generated thereby. - The synergistic effect of the α-phase FAPbI3 perovskite film can be used to obtain high-quality α-phase FAPbI3 perovskite films. In addition, the present invention can further prepare high-efficiency flexible perovskite solar cells in a humid air environment, reduce manufacturing costs, simplify the preparation process, and facilitate the industrial production and commercial application of F-PSCs.

[0027] Compared with the flexible perovskite film prepared in the air in the prior art, the present invention prepares a high-quality pure α-FAPbI3 film in a humid air environment, and the flexible perovskite film is smooth and dense, with a large surface grain size and regular grain edges and corners. The flexible perovskite solar cell prepared in this way has a higher photoelectric conversion efficiency and exhibits better mechanical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the XRD spectrum of the perovskite film prepared in Example 1 of the present invention.

[0029] Figure 2 XRD spectrum of the perovskite film prepared in Comparative Example 1 of the present invention

[0030] Figure 3This is a SEM image of the perovskite film prepared in Example 1 of the present invention.

[0031] Figure 4 This is a SEM image of the perovskite film prepared in Comparative Example 1 of the present invention.

[0032] Figure 5 This is the current density-voltage scanning curve of the flexible perovskite solar cell prepared in Application Example 1 of the present invention.

[0033] Figure 6 This is the current density-voltage scanning curve of the flexible perovskite solar cell prepared in Comparative Example 1 of the present invention.

[0034] Figure 7 This is a curve showing the change in photoelectric conversion efficiency of the flexible perovskite solar cell prepared in Application Example 1 of the present invention as a function of the number of bending times.

[0035] Figure 8 XRD patterns of the perovskite films prepared in Examples 1 to 3. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings.

[0037] In the description of the present invention, unless otherwise specified, all reagents used are commercially available and all methods used are conventional techniques in the art.

[0038] It should be noted that the English name of methylammonium chloride is Methylamine hydrochloride, abbreviated as MACl; the English name of methylammonium thiocyanate is Methylammonium Thiocyanate, abbreviated as MASCN; the English name of methylammonium iodide is Methylammonium iodid, abbreviated as MAI.

[0039] Example 1

[0040] This embodiment provides a method for preparing a flexible perovskite film.

[0041] The following preparation processes were all completed in a high humidity (RH: 60±10%) air environment.

[0042] Step 1: Prepare the covering layer:

[0043] 1.1) Dissolve 5 mg of MACl in 1 mL of isopropanol to obtain a MACl solution, which is referred to as MACl / IPA solution.

[0044] 1.2) Weigh TiO2 colloid and anhydrous ethanol in a mass ratio of 1:4, stir at room temperature for 3 hours to obtain a TiO2 colloid solution.

[0045] 1.3) Place the glass sheet in a cleaning rack, add deionized water, acetone and isopropanol in sequence, and ultrasonicate for 20 minutes each in an ultrasonic cleaner. After cleaning, dry at 70° C. to obtain a pretreated glass sheet.

[0046] 1.4) 60 μL of TiO2 colloidal solution was taken by a pipette and dropped onto the pretreated glass sheet for spin coating deposition; wherein the low speed of the spin coater was 600 rpm, the spin coating time was 6 s, and the high speed of the spin coater was 3000 rpm, the spin coating time was 30 s, and a TiO2 wet film was obtained. The TiO2 wet film was heated at 500°C for 30 min to obtain a glass-TiO2 layer.

[0047] 1.5) Using the glass-TiO2 layer as the substrate, use a pipette to absorb 60 μL of MACl / IPA solution and drop it on the glass-TiO2 layer for spin coating deposition; wherein the low speed of the spin coater is 600 rpm, the spin coating time is 5 s, and the high speed of the spin coater is 4000 rpm, the spin coating time is 30 s, to obtain a covering layer.

[0048] Step 2: Preparation of perovskite film:

[0049] 2.1) Using deionized water, ethanol and isopropanol in sequence, the flexible substrate ITO-PEN was ultrasonically cleaned for 10 minutes in an ultrasonic cleaner, and then treated with ultraviolet ozone for 20 minutes to obtain a pretreated ITO-PEN.

[0050] 2.2) Dilute the SnO2 solution with a concentration of 12% to 5% with deionized water, and then disperse the diluted SnO2 solution in an ultrasonic cleaner for 20 minutes to obtain a dispersed SnO2 solution.

[0051] 2.3) Dissolve 738 mg of lead iodide and 275 mg of formamidine iodide in a mixed solvent of 800 μL of dimethylformamide and 200 μL of N-methylpyrrolidone, and stir at room temperature for 12 h to obtain a perovskite precursor solution, i.e., FAPbI3 solution.

[0052] 2.4) Use a pipette to absorb 60 μL of the dispersed SnO2 solution and drop it on the pretreated ITO-PEN for spin coating deposition; wherein the speed of the spin coater is 4000 rpm and the spin coating time is 30 s. Obtain a SnO2 wet film. Transfer the SnO2 wet film to a hot plate at 150°C for annealing for 30 min to obtain a SnO2-ITO layer, i.e., an electron transport layer.

[0053] 2.5) Taking the electron transport layer as the substrate, 60 μL of FAPbI3 solution was taken by a pipette and dropped on the electron transport layer for spin coating deposition; wherein, the low speed of the spin coater was 600 rpm, the spin coating time was 5 s, and the high speed of the spin coater was 4000 rpm, and the spin coating time was 30 s; when the high speed spin coating was performed for 20 s, 0.5 mL of ethyl acetate was quickly dropped to obtain a perovskite wet film.

[0054] Step 3: Preparation of flexible perovskite film:

[0055] After spin coating, the covering layer was immediately placed on the perovskite wet film to form a closed space, which was then annealed at 70°C for 5 min and then at 100°C for 20 min. After cooling, the glass substrate was peeled off to obtain a flexible perovskite film.

[0056] Example 2

[0057] This embodiment provides a method for preparing a perovskite film.

[0058] The difference between this embodiment and embodiment 1 is:

[0059] In this embodiment, MASCN is used to replace MACl during the preparation of the covering layer.

[0060] Example 3

[0061] This embodiment provides a method for preparing a perovskite film.

[0062] The difference between this embodiment and embodiment 1 is:

[0063] In this embodiment, MAI is used to replace MACl during the preparation of the covering layer.

[0064] Comparative Example 1

[0065] This comparative example provides a method for preparing a flexible perovskite film in air.

[0066] Step 1: Preparation of perovskite precursor solution:

[0067] 738 mg of lead iodide and 275 mg of formamidine iodide were dissolved in a mixed solvent of 800 μL of dimethylformamide and 200 μL of N-methylpyrrolidone, and 40.5 mg of MACl solution was added; wherein the concentration of MACl was 0.6 M, and the solution was stirred at room temperature for 12 hours to obtain a perovskite precursor solution, namely, FAPbI3 solution.

[0068] Step 2: Preparation of flexible perovskite film:

[0069] Taking the electron transport layer as the substrate, 60 μL of FAPbI3 solution was dropped on the electron transport layer for spin coating deposition; wherein, the low speed of the spin coater was 600 rpm, the spin coating time was 5 s, the high speed of the spin coater was 4000 rpm, and the spin coating time was 30 s. When the high speed was spun for 20 s, 0.5 mL of ethyl acetate was quickly dropped, and then annealed at 150 ° C for 20 min to obtain a flexible perovskite film.

[0070] The perovskite film prepared in Comparative Example 1 was used to manufacture a flexible perovskite solar cell according to a conventional method, and the above steps were all completed in the air.

[0071] Application Example 1

[0072] This application embodiment provides a method for preparing a flexible perovskite solar cell.

[0073] S1. Preparation of hole transport layer:

[0074] 1.1) Dissolve 500 mg of lithium bis(trifluoromethanesulfonyl)imide in 1 ml of acetonitrile solution to obtain lithium bis(trifluoromethanesulfonyl)imide acetonitrile solution, referred to as Li-TFSI / acetonitrile solution.

[0075] 1.2) 72.3 mg of 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene was dissolved in 1 ml of chlorobenzene, and 28.8 μL of tert-butylpyridine and 17.5 μL of Li-TFSI solution were added, and stirred at room temperature for 12 h to obtain a mixed solution.

[0076] 1.3) 60 μL of the mixed solution was taken with a pipette and dropped onto the flexible perovskite film prepared in Example 1, and the mixture was spin-coated at 3000 rpm for 30 s. The mixture was placed in a glass culture dish lined with tin foil, and the culture dish was placed in a drying cylinder for 24 h to obtain a hole transport layer.

[0077] S2. Preparation of metal electrode layer: In vacuum evaporation equipment, the parameters are vacuum degree: 10 -3 Pa to 10 -5 Pa, evaporation rate: Substrate temperature: room temperature to 100° C. A silver counter electrode with a thickness of about 100 nm was prepared on the hole transport layer by thermal evaporation to obtain a flexible perovskite solar cell.

[0078] Figure 1 This is the XRD pattern of the flexible perovskite film prepared in Example 1. Figure 1As shown, the XRD peaks of the flexible perovskite film at 14.0°, 28.4° and 31.8° point to the (110), (220) and (310) lattice planes of α-FAPbI3, respectively, and the perovskite film has a strong α phase peak at 14.0° without other impurity peaks. This indicates that the present invention has prepared a high-quality pure α-FAPbI3 perovskite film.

[0079] Figure 2 This is the XRD spectrum of the flexible perovskite film prepared in Comparative Example 1. Figure 2 As shown, the perovskite film prepared in air has a strong α phase peak at 14.0°, but a PbI2 peak at 12.8°, indicating that the perovskite film prepared in air using the traditional method contains PbI2 and the film quality is poor.

[0080] Figure 3 This is a SEM image of the perovskite film prepared in Example 1. Figure 3 As shown, the perovskite film is smooth and dense, with large surface grains and regular grain edges and corners.

[0081] Figure 4 This is a SEM image of the perovskite film prepared in Comparative Example 1. Figure 4 As shown, the perovskite film prepared in air exhibits a discontinuous morphology with numerous pinholes and a large number of small and bright PbI2 particles distributed around the grain boundaries.

[0082] Figure 5 The current density-voltage scanning curve of the flexible perovskite solar cell prepared in Example 1. Figure 5 It can be seen that the short-circuit current of the flexible perovskite battery is 21.52mA / cm 2 , the open circuit voltage is 1.06 V, the fill factor is 77.20%, and the photoelectric conversion efficiency is 17.61%, indicating that the present invention has prepared a high-efficiency flexible perovskite solar cell.

[0083] Figure 6 The current density-voltage scanning curve of the flexible perovskite solar cell prepared in Comparative Example 1. Figure 6 It can be seen that the short-circuit current of the flexible perovskite battery prepared in air is 12.94 mA / cm 2 , the open circuit voltage is 0.71V, the fill factor is 57.35%, and the photoelectric conversion efficiency is 5.27%. Figure 5 The battery data show that the flexible perovskite solar cells prepared in the air using the traditional method have low efficiency and poor photoelectric performance, while the present invention has prepared flexible perovskite solar cells with high efficiency and excellent photoelectric performance in the air.

[0084] Figure 7The curve of the photoelectric conversion efficiency of the flexible perovskite solar cell prepared in Example 1 as a function of the number of bends is shown in FIG. Figure 7 It can be seen that the flexible perovskite battery has good mechanical stability and can maintain the original 85% photoelectric conversion efficiency after 1000 bends.

[0085] Figure 8 The XRD patterns of the perovskite films prepared in Examples 1 to 3 are shown in FIG. Figure 8 As shown, the perovskite films prepared with MACl, MASCN and MAI as covering layers all have strong α-phase peaks at 14.0°, indicating that the three methylamine solutions can be used to prepare perovskite films in air through the confined space annealing strategy described in the present invention. However, compared with MASCN and MAI, the perovskite film prepared with MACl as the covering layer formed by the additive has the strongest peak and the prepared perovskite film has the best quality.

[0086] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, once those skilled in the art know the basic creative concept, they can make other changes and modifications to these embodiments, and these changes and modifications all fall within the scope of the present invention.

[0087] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. If these modifications and variations of the present invention fall within the scope of the equivalent technology of the present invention, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a flexible perovskite film, characterized in that: The following steps are involved: A mesoporous layer is prepared on a rigid substrate, and a methylamine solution is spin-coated on the mesoporous layer to obtain a covering layer; An electron transport layer is prepared on a flexible substrate, a perovskite precursor solution is spin-coated onto the electron transport layer, and a reverse solvent is dropped before the spin coating is completed to obtain a perovskite precursor wet film; The covering layer is covered on the perovskite precursor wet film so that the covering layer and the perovskite precursor wet film form a closed space to block the entry of moisture; at the same time, through annealing treatment, the perovskite film is obtained under the auxiliary nucleation and diffusion recrystallization of the covering layer; after cooling, the hard substrate is removed to obtain a flexible perovskite film on the flexible substrate.

2. The method for preparing a flexible perovskite film according to claim 1, characterized in that: The annealing treatment is performed at a temperature of 70°C to 100°C.

3. The method for preparing a flexible perovskite film according to claim 1, characterized in that: The concentration of the methylamine solution is 4.9 mg / mL to 5.1 mg / mL; The methylamine solution is methylammonium chloride solution, methylammonium iodide solution or methylammonium thiocyanate solution; The methylamine solution is prepared by dissolving methylammonium chloride, methylammonium iodide or methylammonium thiocyanate in isopropanol.

4. The method for preparing a flexible perovskite film according to claim 1, characterized in that: The mesoporous layer is a TiO2 layer, and the thickness of the mesoporous layer is 50nm-100nm.

5. The method for preparing a flexible perovskite film according to claim 1, characterized in that: The perovskite precursor solution is composed of a solute and a solvent; Among them, the solutes include formamidine halides and lead salts; The solvents are dimethylformamide and N-methylpyrrolidone; The concentration of the perovskite precursor solution is 1 mol / L to 2 mol / L.

6. The method for preparing a flexible perovskite film according to claim 1, characterized in that: The flexible substrate is an ITO-PEN or FTO-PEN transparent electrode, and the rigid substrate is glass.

7. The method for preparing a flexible perovskite film according to claim 1, characterized in that: The reverse solvent is ethyl acetate.

8. A flexible perovskite film prepared by the method for preparing a flexible perovskite film according to any one of claims 1 to 7.

9. A flexible perovskite solar cell, characterized in that: It contains the flexible perovskite film as described in claim 8; the flexible perovskite solar cell also includes a hole transport layer and a metal electrode, the hole transport layer is located on the flexible perovskite film, and the metal electrode is located on the hole transport layer.

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